This invention relates to methods and apparatus for gas flush treatment of fresh leafy produce in a vacuum chamber. More particularly, the invention relates to methods and apparatus for flushing one or more containers of fresh, leafy produce with one or more gases such as nitrogen in a vacuum chamber utilizing, on each of said containers, a closure system that can be attached to and detached from such a container. This system includes a closure that opens inside a vacuum chamber when the pressure inside the chamber is reduced below atmospheric pressure, and closes when the pressure inside the chamber is at or near atmospheric pressure.
The closure system is of a size and shape adapted for attachment to the opening at the top of containers of fresh leafy produce. Each of these containers preferably includes a liner bag to hold such produce. For attachment to each of these bags, the closure system includes a body portion, a closure connected to the body portion, and a mechanism connected to the closure and to the body portion that moves the closure from an open position to a closed position, and vice versa. This mechanism includes a sealed container, such as a bellows or bladder, of gas, e.g. air preferably at a pressure at or near to atmospheric pressure. This sealed container is connected to one or more arms that move the closure between open and closed positions when the gas inside the sealed container expands or contracts. Expansion and contraction occurs, for example, as the pressure in a vacuum chamber containing produce containers with attached closure systems falls from or rises to atmospheric pressure.
In preferred embodiments, the mechanism includes a first arm movably connected at one end to the internal side wall of the body portion, and to the sealed container at the other end, and a second arm movably connected to the inner surface of the closure at one end, and to the sealed container at the other end. The closure can be hinged to the body portion of the closure device, or can be attached to the inner surface of the body portion. Contraction of the gas inside the sealed container moves these arms and the connected closure to the closed position. Expansion of the gas inside the container moves these arms and connected closure to the open position.
The body portion has a size and shape adapted to be removably attached to the open end of a container of fresh produce. The body portion preferably includes a cylindrical, proximal portion connected to the closure at one end, and a distal portion that fits on or over a produce container.
In operation, a closure system is sealingly attached, by twist-ties, tape or otherwise, to the top of a container of fresh produce. Each container with its attached closure system is placed into a vacuum chamber, and the vacuum chamber is closed to the outside atmosphere. A vacuum is drawn upon the interior of the chamber, reducing the pressure on each container within the chamber. As the pressure drops below atmospheric pressure inside the chamber, the air inside the sealed container of each mechanism expands, moving the closure to an open position. Upon opening, the pressure inside each of the containers of fresh produce falls to the pressure within the chamber itself.
When the pressure inside the chamber and each container has reached a desired level, the chamber is filled with a desired gas e.g. nitrogen, or a gas mixture, until the pressure inside the chamber, and inside each container inside the chamber, rises to or near atmospheric pressure. At this pressure, the sealed container connected to each arm mechanism contracts, moving the closure of each closure system to a closed position, trapping the desired gas atmosphere inside each produce container.